The partial base sequences of 18S and 26S rRNAs were examined in eighteen strains of Debaryomyces, Torulaspora, and Yamadazyma species including two strains of D. udenii. All of the strains of Debaryomyces species constituted a single group (cluster) phylogenetically. In the partial base sequence (positions 493 through 622, 130 bases) of 26S rRNA, the maximum homologies were 79-99% among Debaryomyces species. T. globosa and Y. philogaea had 71-78% and 81-87% maximum homologies, respectively, with Debaryomyces species. In the partial base sequence (positions 1611 through 1835, 225 bases) of 26S rRNA, the base differences numbered 5-0 among Debaryomyces species. T. globosa and Y. philogaea had 15-13 and 10-8 base differences, respectively, with Debaryomyces species. In the partial base sequence (positions 1451 through 1618, 168 bases) of 18S rRNA, Debaryomyces species were divided into two subgroups (subclusters). The first subgroup was comprised of D. hansenii, D. melissophilus, D. udenii, and so on, and the second subgroup comprised of D. castellii, D. polymorphus, D. yamadae, and so on. The base difference numbered 1 between the two subgroups. T. globosa and Y. philogaea had 5-4 and 1-0 base differences, respectively, with Debaryomyces species. Between T. globosa and S. cerevisiae, there was 1 base difference. D. tamarii occupied a distant position (maximum homologies, 63-71%; base differences, 50-48 and 20-19, respectively).